/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    SplitEvaluator.java
 *    Copyright (C) 1999-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.experiment;

import java.io.Serializable;

import weka.core.Instances;

/**
 * Interface to objects able to generate a fixed set of results for a particular
 * split of a dataset. The set of results should contain fields related to any
 * settings of the SplitEvaluator (not including the dataset name. For example,
 * one field for the classifier used to get the results, another for the
 * classifier options, etc).
 * <p>
 *
 * Possible implementations of SplitEvaluator: <br>
 * <ul>
 * <li>StdClassification results
 * <li>StdRegression results
 * </ul>
 *
 * @author Len Trigg (trigg@cs.waikato.ac.nz)
 * @version $Revision$
 */
public interface SplitEvaluator extends Serializable {

    /**
     * Sets a list of method names for additional measures to look for in
     * SplitEvaluators.
     * 
     * @param additionalMeasures a list of method names
     */
    void setAdditionalMeasures(String[] additionalMeasures);

    /**
     * Gets the names of each of the key columns produced for a single run. The
     * names should not contain spaces (use '_' instead for easy translation.) The
     * number of key fields must be constant for a given SplitEvaluator.
     *
     * @return an array containing the name of each key column
     */
    String[] getKeyNames();

    /**
     * Gets the data types of each of the key columns produced for a single run. The
     * number of key fields must be constant for a given SplitEvaluator.
     *
     * @return an array containing objects of the type of each key column. The
     *         objects should be Strings, or Doubles.
     */
    Object[] getKeyTypes();

    /**
     * Gets the names of each of the result columns produced for a single run. The
     * names should not contain spaces (use '_' instead for easy translation.) The
     * number of result fields must be constant for a given SplitEvaluator.
     *
     * @return an array containing the name of each result column
     */
    String[] getResultNames();

    /**
     * Gets the data types of each of the result columns produced for a single run.
     * The number of result fields must be constant for a given SplitEvaluator.
     *
     * @return an array containing objects of the type of each result column. The
     *         objects should be Strings, or Doubles.
     */
    Object[] getResultTypes();

    /**
     * Gets the key describing the current SplitEvaluator. For example This may
     * contain the name of the classifier used for classifier predictive evaluation.
     * The number of key fields must be constant for a given SplitEvaluator.
     *
     * @return a value of type 'Object'
     */
    Object[] getKey();

    /**
     * Gets the results for the supplied train and test datasets.
     *
     * @param train the training Instances.
     * @param test  the testing Instances.
     * @return the results stored in an array. The objects stored in the array may
     *         be Strings, Doubles, or null (for the missing value).
     * @exception Exception if a problem occurs while getting the results
     */
    Object[] getResult(Instances train, Instances test) throws Exception;

    /**
     * Returns the raw output for the most recent call to getResult. Useful for
     * debugging splitEvaluators.
     * 
     * @return the raw output corresponding to the most recent call to getResut
     */
    String getRawResultOutput();

} // SplitEvaluator
